Database recovery using persistent address spaces

ABSTRACT

A processor(s) initiates a database transaction, in a computing environment that includes a database that includes one or more memory devices. The processor(s) forks a first address space that represents a current state of the database, to create a second address space. The processor(s) writes an entry indicating timing of the initiating to a log file and generates a file that is mapped to the one or more memory devices. The file includes differences in state between the current state of the database and a state subsequent to executing and committing the database transaction, and a timestamp indicating timing for committing the database transaction. The processor(s) write the database transaction to the second address space.

BACKGROUND

For ACID (Atomicity, Consistency, Isolation, Durability) transactionsemantics in (relational) databases, with UNDO/REDO information storedin BEFORE/AFTER images for atomicity (i.e., rollback capability) anddurability, it is often problematic to process mass updates to thedatabase as needed for ELT/ETL (Extract, Transform, Load) processes orfor a re-load into an accelerator. Because writing log information cancause significant overhead, among other issues, especially if many writeoperations are outstanding, performing COMMITs frequently isrecommended, which can affect the efficiency of the database.

SUMMARY

Shortcomings of the prior art are overcome and additional advantages areprovided through the provision of a method of processing a transactionin a database. The method includes, for instance: initiating, by one ormore processors, a database transaction, in a computing environmentcomprising a database comprising one or more memory devices, wherein theinitiating comprises: forking, by the one or more processors, a firstaddress space, wherein the first address space is an address spacerepresenting a current space of the database, to create a second addressspace; writing, by the one or more processors, an entry indicatingtiming of the initiating to a log file; and generating, by the one ormore processors, a file, wherein the file is mapped to the one or morememory devices, the file mapping a state of the database comprising oneor more temporary modifications implemented by the database transactionand a timestamp indicating timing for committing the databasetransaction; and writing, by the one or more processors, the databasetransaction to the second address space.

Methods and systems relating to one or more aspects are also describedand claimed herein. Further, services relating to one or more aspectsare also described and may be claimed herein.

Additional features are realized through the techniques describedherein. Other embodiments and aspects are described in detail herein andare considered a part of the claimed aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more aspects are particularly pointed out and distinctly claimedas examples in the claims at the conclusion of the specification. Theforegoing and objects, features, and advantages of one or more aspectsare apparent from the following detailed description taken inconjunction with the accompanying drawings in which:

FIG. 1 depicts a workflow that includes various aspects of a datarequest in some embodiments of the present invention;

FIG. 2 illustrates a technical architecture of a computing system wherecertain aspects of embodiments of the present invention may beimplemented;

FIG. 3 illustrates a snapshot in a technical environment in whichaspects of some embodiments of the present invention have beenimplemented;

FIG. 4 illustrates a snapshot in a technical environment in whichaspects of some embodiments of the present invention have beenimplemented;

FIG. 5 illustrates a snapshot in a technical environment in whichaspects of some embodiments of the present invention have beenimplemented;

FIG. 6 depicts a workflow that includes various aspects of a datarequest in some embodiments of the present invention;

FIG. 7 depicts one embodiment of a computing node that can be utilizedin a cloud computing environment;

FIG. 8 depicts a cloud computing environment according to an embodimentof the present invention; and

FIG. 9 depicts abstraction model layers according to an embodiment ofthe present invention.

DETAILED DESCRIPTION

The accompanying figures, in which like reference numerals refer toidentical or functionally similar elements throughout the separate viewsand which are incorporated in and form a part of the specification,further illustrate the present invention and, together with the detaileddescription of the invention, serve to explain the principles of thepresent invention. As understood by one of skill in the art, theaccompanying figures are provided for ease of understanding andillustrate aspects of certain embodiments of the present invention. Theinvention is not limited to the embodiments depicted in the figures.

As understood by one of skill in the art, program code, as referred tothroughout this application, includes both software and hardware. Forexample, program code in certain embodiments of the present inventionincludes fixed function hardware, while other embodiments utilized asoftware-based implementation of the functionality described. Certainembodiments combine both types of program code. One example of programcode, also referred to as one or more programs, is depicted in FIG. 7 asprogram/utility 40, having a set (at least one) of program modules 42,may be stored in memory 28.

Embodiments of the present invention include a method, a system, and acomputer program product that enable one or more programs executing onone or more processors to process a database transaction. The disclosedmethod of processing enabled by the method, computer program product,and system provides certain advantages over current processing systemsand methods. Some advantages of embodiments of the present invention arethe elimination of certain processes that can stall efficiency andcompromise data integrity, while others represent the introduction offunctionality that is not available in current systems. The newfunctionality positively impacts the efficiency and efficacy of thedatabase.

Some embodiments of the present invention improve processing byeliminating current realities that hinder efficiency and efficacy incurrent systems. For example, in current database systems, ifmaintaining data consistency and serializability are required, and thisaccomplished by using lock-based methods, the scalability of thedatabase system is significantly reduced. This reality is experienced,for example, when a long-running transaction is holding a write lock. Tomaintain the aforementioned consistency and serializability, somecurrent systems utilize multi-version concurrency control (MVCC) basedmechanisms together with conflict detection, using directed graphtraversal. When compared to embodiments of the present invention, thesesystems process transactions less efficiently because in these currentsystems, each read transaction is slightly slowed down due to MVCCrelated overhead caused by the fact that in order to figure out whichparts of the data are valid at a certain point in time, all data has tobe processed. An aspect of some embodiments of the present inventionprovides an advantage (e.g., when processing business-analytics-relatedworkloads) over these current systems in that, in these embodiments, nolocking/serialization effects/scalability limits are introduced and alltransactions can be processed at full speed, as if no concurrencycontrol logic is in place.

Some embodiments of the present invention also provide advantages overthe logical unit of work (LUW) implementations in current system. Forexample, in these current systems, customers are forced, for technicalreasons, to commit frequently, rather than because the business logic oftransaction processing dictates the commits, which can create highprocessing costs. The frequency of committing for technical reasons isbecause state-of-the-art relational databases using locking basedconcurrency control cannot handle with too many open transactions. Anadvantage of some embodiments of the present invention is theelimination of the frequency requirement for committing transactions,without compromising performance or data integrity.

Some embodiments of the present invention improve transaction processingin databases by providing aspects that are not available in currentsystems. For example, not only do certain embodiments of the presentinvention provide trivial backups, where the program code duplicatesjust the latest file, embodiments of the present invention also providetrivial recoveries, where the program code reads just the latest file torestore the database to a desired state. Additionally, some embodimentsof the present invention provide ease in adding replication with minimaldelay and high efficiency. Another advantageous aspect of certainembodiments of the present invention is the introduction of what can beunderstood as a temporary Extract, Load, Transform, (ELT) functionality.In general, ELT, which is a variation of Extract, Transform, Load (ETL),allows raw data to be loaded directly into a target and transformedthere. In embodiments of the present invention, the temporary ELT aspectprovides for an analyst to work on data, based on private snapshot ofthe enterprise database, performing all appropriate activitiesin-database. The program code can then discard the results of theseactivities and the private snapshot using ROLLBACK, after reportcreation is complete.

As will be understood from the description and figures, transactionprocessing in embodiments of the present invention has somecommonalities as well as some differences when compared to currenttransactions processing technologies. For example, unlike many currentmethods, in some embodiments of the present invention, at every newwrite transaction, the program code either creates a new file and/orcompresses the differences (i.e., deltas) in a special file system(e.g., FIGS. 3-5, memory mapped files 270 370 470), for performanceoptimization. Similar to standard MVCC processing, in some embodimentsof the present invention, the program code utilizes groom processes todelete or discard outdated blocks. However, in embodiments of thepresent invention, the grooming process is simplified, when comparedwith current systems. As understood by one of skill in the art, programcode executing a grooming process maintains the user tables byreclaiming disk space for deleted or outdated rows and reorganizes thetables by their organizing keys. Specifically, the program codeprocesses and reorganizes table records in each data slice in a seriesof steps. Grooming deleted records removes records that were alreadylogically deleted. Finally, some embodiments of the preset inventionenable different database usage by maintaining all currently activeversions in file-backed main memory, with copy-on-write (e.g., FIG. 4address spaces 430 c-430 e). All versions that are not groomed areeasily recoverable and/or available. Because not all versions arein-memory on all nodes, limitations may exist on options to usescale-out and/or cluster, if single-node memory capacity is a concern.

FIG. 1 provides a high level workflow 100 of certain aspects of someembodiments of the present invention. In general, aspects of embodimentsof the present invention generate a memory-mapped address space with aclone (i.e., “fork”) capability, which enables the memory and the diskof a database, which can be comprised of multiple computing nodes, tostore tables, optionally together with index structures. Generally,forking is a functionality that is used to generate a duplicate ofparticular process by creating two simultaneous executing processes of aprogram. These two processes are typically called the “parent” and“child” processes. These processes then use multitasking protocols toshare system resources. When forking is implemented, a copy-on-writesystem used to store progressive changes to a process after forking.Typically, static code is not duplicated, but shared. At the time that aprocess modifies shared code, the changes are created and storedseparately in order to promote efficiency in the use of forkedprocesses. Developers also have to be aware of some issues with usingfork to generate a duplicate process. One of these is the issue ofmultithread programs; because the child process only inherits a singlethread, there can be problems related to what happens to multiplethreads when the fork function is called. These and other considerationsare often mentioned by those who have worked with the fork function.

When one or more programs in the database receives a new read or writetransaction, the one or more programs clone the address space, withcopy-on-write timing and dirty pages, supported by the memory managementunit (MMU) of the processor and by the operating system (OS). When theone or more programs receive a command to commit the transaction, theone or more programs close the database file and make the copy of theaddress space with the committed transaction the new master (as opposedto the cloned) address space. This newly minted master comprises alatest consistent state of the database.

As illustrated in FIG. 1, in embodiments of the present invention, inorder to process a database transaction, one or more programs, executingon one or more processors, maintain a current version of at least a partof the database in a file associated with a mass storage device (110).

The one or more programs map at least a portion of the content of thefile to a processor address region of a processor(s) (120). Based onreceiving a database command to open a new transaction, the one or moreprograms generate a cloned (i.e., “forked”) version of the addressregion (130). The one or more programs manage the cloned version of theaddress space according to a copy-on-write strategy. The one or moreprograms write operations belonging to the transaction on this clonedversion of the address space. In some embodiments of the presentinvention, as part of establishing the cloned version of the addressregion, the one or more programs map one or more files associated with amass storage device comprising the database to the cloned version of theaddress space (140). The files map the current state of the database,including all temporary modifications done by transactions owning thepersistent address space. Each mapped file represents the database spacefrom given transaction's perspective (with the file making that addressspace persistent). In some embodiments of the present invention, thereis one memory mapped file with directly associated memory contents forevery new write transaction.

Depending upon commands received, the fate of the cloned versionchanges. Based on receiving a command to commit the transaction, the oneor more programs determine that the cloned version of the address spaceand the mapped file(s) and the one or more files associated with a massstorage device, reflect a new current version of the at least a part ofthe database (150 a). Meanwhile, based on receiving a command to rollback the transaction, the one or more programs discard the clonedversion of the address and the one or more files associated with a massstorage device (150 b).

FIG. 2 is an overview of an example of a technical architecture 200 intowhich certain aspects of some embodiments of the present invention maybe implemented. The architecture 200 includes an MMU of a processor 210that includes a translation lookaside buffer (TLB) 220 that mapsaddresses that represent memory areas where contents are absolutelyplaced (e.g., A1, A2, A2 b) to placements in sections and blocks of aparticular memory regions, persistent address spaces (e.g., P1, P2, P3).In general, an MMU 210 maps a logical address to a physical address. TheMMU 210 is communicatively coupled to address spaces, in this example, afirst address space 230 a, and a second address space 230 b.

As illustrated in FIG. 1, each address space includes addresses thatrepresent memory areas where contents are absolutely placed. The firstaddress space 230 a, includes addresses A1 and A2. The second addressspace 230 b, includes addresses A1 and A2 b. A2 b, is so-named as it isa backup copy on A2.

The MMU 210 is also communicatively coupled to persistent storage 240.As indicated in FIG. 1, persistent storage 240 may be, but in notlimited to, a solid state drive. The persistent storage 240 is comprisedof the particular memory regions (e.g., P1, P2, P3). Files withdirectory entries 250 indicate the lines (L1, L2, L2 b) at which thephysical addresses or memory regions (e.g., P1, P2, P3) addressed in theaddress spaces 230 a 230 b, are located. A log file 260 indicates theprocessing of a transaction by the technical architecture 200. Asindicated in the log file 260 and the file directory entries 250 forfile 1, file 1 is memory mapped to the persistent storage 240. As notedin the log file 260, a transaction is identified by an identifier (i.e.,tid1). The program code commits the transaction (i.e., tid1) at a giventime (i.e., time2), and a given (memory mapped) file (i.e., file1).Another transaction begins at another time (i.e., transaction=tid2,time=time3). The program code commits the next transaction (i.e., tid2)at another time (i.e., time4), with another file (i.e., file2).

FIGS. 3-5 show the progression of transactions that are processed inaccordance with aspects of some embodiments of the present invention,when contrasted with transactions that are processed using currentmethods. The limitations in this environment, including, the number ofmemory modules, segments, address spaces, etc., are offered merely forillustrative purposes and do not represent limitations to technicalarchitectures into which aspects of the present invention may beimplemented.

FIG. 3 illustrates a snapshot 300 of database transactions in atechnical environment. Referring to FIG. 3, modules in a main memory 315(i.e., M1, M2, M3, M4, and M5) and segments in the external memory 325(i.e., S1, S2, S3, S4, S5, and S6), comprise portions of the addressesin the address spaces 330 a 330 b 330 c. The addresses also include aline designation (i.e., L1, L2, L3, and L4). Thus, the format for agiven address is “Lx Mx Sx” with an x being replaced by an integeridentifying a memory portion. Three address spaces contain addresses,including a first address space 330 a, a second address space 330 b, anda third address space 330 c. The third address space 330 c is the newestcommitted address space.

In an aspect of some embodiments of the present transaction, the programcode generates (and/or updates) at least one a memory mapped file 370that represents each transaction. As illustrated in FIG. 3, when theprogram code starts a new read-write transaction, the program codeappends a time stamp and a transaction number to a log file 360. Forexample, the first line of the log file 360 is “T0: BOT T1”(BOT=beginning of transaction). This line indicates that the programcode started executing transaction T1 (i.e., opened transaction T1) attime t0/T0. Also as part of commencing a transaction, as will bedescribed in more detail herein, the program code clones (forks) theaddress space that represents the latest commit state. The snapshot 300of FIG. 3 represents a state where transactions T1, T2, and T3 have allbeen executed and committed. Thus, the program code has generated amemory mapped file 370 designating changes to address values thatcomprise each transaction, and timestamped, in the log file 360, bothexecuting and committing the transactions.

The log file 360 of FIG. 3 chronicles the transactions illustrated bythe address spaces 330 a 330 b 330 c. The third address space 330 c inFIG. 3 is marked as the newest committed address space, because, asenumerated in the log file 360, and addressed in greater detail below,the contents of the first address space 330 a and the second addressspace 330 b were previously committed, at the time of the snapshot 300that is FIG. 3.

Based on the log file 360, the program code has executed threetransactions, T1, T2, and T3. At a time of t0, program codeinitiated/opened transaction T1 and generated the memory mapped file,File 1. At time t1, transaction T1, the program code committed T1. Attime t2, the program code initiated transaction T2, and generated memorymapped file, File 2. At time t3, the program code committed transactionT2. At time t4, the program code initiated transaction T3, and at timet5, the program code committed transaction T3. At t3, the program codealso generated the memory mapped file, File 3. Thus, as discussedrelative to existing transaction processing methods, the program codeinitiates and then commits each transaction. Aspects of embodiments ofthe present invention eliminate the necessity of committing sofrequently, which is further demonstrated in FIG. 4.

Returning to FIG. 3, the log file, and the first address space 330 ainclude addresses for L1 and L2, the specifics of which are reproducedbelow.

L1 M1 S1

L2 M2 S2

The memory mapped file that coordinates with transaction T1, File 1,contains these values for S1 and S2. At time t1, the segments, asreflected in the first address space, for L1 and L2, are S1 and S2. Inthis example, the memory modules in the main memory 415 are logicallycoordinated with the segments, in the illustrative technicalenvironment. Thus, when the segment for a line changes in an address, sodoes not module.

Upon commencement of transaction T2, the program code generated thememory mapped file File 2. The second address space 330 b, created bythe program code when executing transaction T2, includes lines insegments S1, S2, S3, and S4. When executing transaction T2, the programcode cloned the first address space 330 a, which at the time was themost current committed address space, to generate the second addressspace 330 b. The memory mapped file for the transaction T2, indicatesthat in executing transaction T2, the program code added addressesreferencing S3 and S4, to the second address space 330 b. The programcode updated made this addition/change to the cloned address space, thesecond address space 330 b. The contents of the second address space 330b, based on the program code executing the transaction T2, arereproduced below:

L1 M1 S1

L2 M2 S2

L3 M3 S3

L4 M4 S4

At the time that the program code executed the third transaction T3, thesecond address space 330 b was the most recently committed addressspace. As indicated in the log file 360, after initiating thetransaction that generated the second address space 330 b, the programcode committed the second address space 330 b. However, upon conclusionof the transaction executed in this figure, per the log file 360, thethird address space 330 c, is the newest committed address space, andincludes lines in segments S5, S2, S3, and S6. As illustrated in the logfile 360 and the transaction 370 details, the program code initiatestransaction T3 to clone the second address space 330 b and generatesmemory mapped File 3. The clones address space, the third address space330 c, which contains addresses on lines L1, L2, L3, and L4. The programcode executes the transaction T3 and makes changes in the third addressspace 330 c, updating certain values in the third address space 330 c.Transaction T3 (as seen in memory mapped file, File 3), updates L1 andL4. The contents of the third address space 330 c after T3 was executedare reproduced below:

L1 M5 S5

L2 M2 S2

L3 M3 S3

L4 M6 S6

The final action in the log file 360 is committing transaction T3. Thus,at the conclusion of the transactions in the log file 360, the thirdaddress space 330 c is the newest committed address space, as designatedin the snapshot 300.

Referring to FIG. 4, the snapshot 400 pictured, as seen in the log file460, was taken after two additional transactions, T4 and T5, wereexecuted by one or more processors, but no additional transactions werecommitted. In this snapshot 400, the third address space 430 c (330 c inFIG. 3), remains the newest committed address space. Unlike in FIG. 3,the third address space 430 c is not the newest address space, but it isthe newest address space that has been committed. As indicated in thelog file 460, the program code executed but did not commit thetransactions that generated the fourth address space 430 d and the fifthaddress space 430 e (i.e., transaction T4 and transaction T5). Thus,when initiating transaction T4 and transaction T5, the program codecloned (i.e., forked) the third address space 430 c because the thirdaddress space 430 c is the newest committed address space.

In FIG. 4, the program code generates the fourth address space 430 d byinitiating the transaction T4 and generating a memory mapped file, File4. File 4, as seen in the transaction 470, includes references tosegments S7, S2, S3, and S8, in that order. The timestamp on File 4 ist8, indicating timing for changes in this memory mapped file related totransaction to be relevant to the state of the database. The log file460 indicates that the program code opened transaction T4, cloned thethird address space 330 c, wrote a memory mapped file, File 4, and inexecuting the transaction T4, updated the first address, the addressstarting with L1, with segment S7 (and the module M7). Below are thecontents of the fourth address space 430 d (a clone of the third addressspace 430 c) after the program code has executed the transaction T4:

L1 M7 S7

L2 M2 S2

L3 M3 S3

L4 M6 S6

As seen in the log file 406, although the program code executedtransaction T4 (i.e., BOT T4), the program code did not commit thistransaction after execution. Thus, despite the third address space 430 chaving been cloned to create the fourth address space 430 d, the thirdaddress space 430 c is still the newest committed address space.Therefore, the program code will clone the third address space 430 cwhen executing the next transaction, in this example, transaction T5.

In executing transaction T5, based on the third address space 430 cbeing the newest committed address space, when executing transaction T5,the program code clones the third address space 430 c, to generate thefifth address space 430 e. As with the other transactions, as part ofexecuting the transaction T5, the program code generates a memory mappedfile, File 5. The program code executes the transactions, details ofwhich are entered in File 5, which include the segment values S6, S2,S3, and S8. Thus, to generate the resultant address space, the fifthaddress space 430 e, the program code updates the M and S value in theaddress designated L4. Below are the resulting contents of the fifthaddress space 430 e after the program code has executed (but notcommitted), as indicated by the log file 460, transaction T5.

L1 M5 S5

L2 M2 S2

L3 M3 S3

L4 M8 S8

As indicated in the third address space 430 c, the first address,originally L1 M5 S5, was updated in the fourth address space 430 d to L1M7 S7, so the fourth address space contains the most recent data relatedto this address. Meanwhile, the fourth address in the third addressspace 430 c, originally L4 M6 S6, was updated by the fifth addressspace, to L4 M8 S8, so the fifth address space contains the most recentdata related to this address.

FIG. 5 is a snapshot taken after the program code has committed thefourth address space 530 d (e.g., FIG. 4, 430 d). Thus, the fourthaddress space 530 d is the newest committed address space and will bethe parent address space that the program code will clone when opening anew transaction. At demonstrated in the log file 560, at time T8/t8, theprogram code committed the fourth transaction T4 as well as the memorymapped file, File 4. To commit the fourth transaction, T4, the programcode references the most current cloned address space, the fifth addressspace 530 e, and the memory mapped file for transaction T4, File 4.Referencing the memory mapped file, File 4, shows the program code thatthe address beginning L4 was updated since T4 was executed (bytransaction T5). Thus, the memory mapped file, File 4, with thetimestamp of t8, the same timestamp as when the program code committedtransaction T4, is relevant to the current state of the database. Uponthe program code committing the fourth address space 530 d, this addressspace becomes the newest current address space. As seen in the log file560, upon committing the transaction T4, the program code performed anatomic (serialized) operation to append a file name (e.g., File 4) withthe transaction (e.g., T4) start and/or transaction end time stamps(e.g., T8), to log file.

The transactions in FIGS. 3-5 are read-write transactions. Aspects ofsome embodiments of the present invention also provide for thegeneration of read-only transactions. For example, in an embodiment ofthe present invention, program code starts a read-only transaction witha new thread of address space with the latest commit state.

FIG. 6 provides a more detailed workflow 600 of various aspects of someembodiments of the present invention. In an embodiment of the presentinvention, the program code starts a read-write transaction by appendinga time stamp and transaction number to a log file (610) (e.g., FIG. 4,460, “T6: BOT T4”). The program code forks the address space with thelatest commit state and generates a new memory mapped file to capturethe differences between the latest commit state before and afterexecuting of the transaction (620). In another embodiment of the presentinvention, rather than generate a new file for each transaction, theprogram code compresses deltas (between transactions) in a special filesystem, for performance optimization.

In some embodiments of the present invention, the program code maintainsactive versions of the address space in file-backed main memory, withcopy-on-write timing (630). The program code may utilize a number ofdifferent approaches to copy-on-write in order to maintain dataintegrity, as the pages can be dirty. In some embodiments of the presentinvention, the program code makes a note on a changed memory block andperform a conflict check when committing the transaction. The programcode may also utilize a traditional two phase lock (2PL) approach andlock the block that is to be updated in the current addressspace-related data structure. The program code can wait if an exclusivelock is not available. The program code may also rely on MVCC semantics,which do not require utilizing a log file and may additionally check forcycles at commit time in order to diminish the possibility of potentialinconsistencies.

In an embodiment of the present invention, the program code performs awrite of the transaction in the new (private) address space with thememory mapped file (640). The program code commits the transaction(650). As discussed above and illustrated in the FIGS. 3-5, the programcode may commit a transaction immediately after writing it, or at somefuture time. As part of committing the transaction, based on the programcode writing something to disk when committing the transaction, theprogram code closes the new file, verifies that all data persisted ondisk, and identifies any changed blocks (653). The program code thenperforms an atomic (serialized) operation and appends the new file namewith the transaction start and/or transaction end time stamps to logfile (655). The program code establishes the (cloned) address space(with the writes from the transaction execution), as the new currentaddress space (658). The new address space is provided with specialtreatment if multiple blocks have been updated concurrently.

Among the advantages of aspects of various embodiments of the presentinvention are the simplicity with which certain basic activities can beaccomplished. In response to obtaining an instruction to roll back thetransaction, the program code discards the memory mapped file and the(cloned) address space (not pictured). Embodiments of the presentinvention simplify recovery to the latest consistent state of thedatabase. To recover to a latest consistent state, the program codereads the latest file using a memory-mapped file I/O. To initiate apoint-in-time recovery or a transaction restart, the program codeidentifies a related file name for that point or transaction in time inlog file. The program code reads the identified file using amemory-mapped file I/O. Aspects of some embodiments of the presentinvention also simplify the creation of a backup or a snapshot of thedatabase. To create a backup or snapshot, the program code duplicates afile, copying all referenced blocks for the backup and usingcopy-on-write to generate a snapshot. As illustrated in FIG. 6, atransaction being left in an uncommitted/open state does not interferewith other transactions being started afterwards. In some embodiments ofthe present invention, one or more programs could page out anot-committed transaction completely to archive storage and continueworking on it later, even a few months later (e.g., after a user workingwith a special report continues that work), by just re-loading thepersistent address space because no later address space depends on it.

Embodiments of the present invention include a computer-implementedmethod, a computer program product, and a computer system for processingdatabase transactions. Some embodiments of the present invention includeone or more programs initiating a database transaction, in a computingenvironment that include a database that includes one or more memorydevices. Initiating the transaction includes the one or more programsforking a first address space, where the first address space is anaddress space representing a current state of the database, to create asecond address space. The one or more programs write an entry indicatingtiming of the initiating to a log file. The one or more programsgenerate a file, where the file is mapped to the one or more memorydevices. The file includes: 1) differences in state between the currentstate of the database and a state subsequent to executing; and 2)committing the database transaction and a timestamp indicating timingfor committing the database transaction. The file maps a state of thedatabase comprising one or more temporary modifications implemented bythe database transaction and a timestamp indicating timing forcommitting the database transaction. The one or more programs write thedatabase transaction to the second address space.

In some embodiments of the present invention the one or more programsutilize copy-on-write timing, to maintain the address space and thesecond address space.

In some embodiments of the present invention, the one or more programscommit the database transaction to the one or more memories, whichincludes the one or more programs writing data to the one or more memorydevices. The one or more programs append the log file with an identifierof the file and a timestamp; the timestamp represent the transactionstart time or end time. The one or more programs replace the firstaddress space with the second address space, where based on thereplacing, the second address space is the address space representingthe current state of the database.

In some embodiments of the present invention, the one or more programsinitiate a new database transaction, which includes the one or moreprograms forking the second address space to create a third addressspace. The one or more programs write a new entry indicating timing ofthe initiating to a log file. The one or more programs generate a newfile; the new file is mapped to the one or more memory devices. The newfile includes: 1) differences in state between the current state of thedatabase and a state subsequent to executing and committing the newdatabase transaction; and 2) a new timestamp indicating timing forcommitting the new database transaction. The file maps a new state ofthe database comprising one or more temporary modifications implementedby the new database transaction and a new timestamp indicating timingfor committing the new database transaction. The one or more programswrite the new database transaction to the third address space.

In some embodiments of the present invention, the one or more programsrestore the current state to a given point-in-time, with the givenpoint-in-time being represented by the timestamp. The one or moreprograms access the log file to identify a record with the timestamp,where the record includes the identifier of the file. The one or moreprograms read the file utilizing a memory mapped input/output device todetermine differences between the current state and a state at the givenpoint-in-time. The one or more programs execute one or moretransactions, to restore the current state to the state at the givenpoint-in-time.

In some embodiments of the present invention, the one or more programsutilize the file to verify that the data persisted in the one or morememories. The one or more programs also identify any changes blocks inthe one or more memories.

In some embodiments of the present invention, the one or more programsreceive an instruction to roll back the transaction. The one or moreprograms discard the second address space and the file.

In some embodiments of the present invention, the one or more programsrecover a latest consistent state of the database, which includes theone or more programs reading the file utilizing a memory mappedinput/output device to determine differences between the current stateand a state reflected in the file. The recovering also includes the oneor more programs executing one or more transactions, to restore thecurrent state to the state a state reflected in the file.

Referring now to FIG. 7, a schematic of an example of a computing node,which can be a cloud computing node 10. Cloud computing node 10 is onlyone example of a suitable cloud computing node and is not intended tosuggest any limitation as to the scope of use or functionality ofembodiments of the invention described herein. Regardless, cloudcomputing node 10 is capable of being implemented and/or performing anyof the functionality set forth hereinabove. In an embodiment of thepresent invention, elements of the technical environment of FIG. 2, canbe understood as cloud computing node 10 (FIG. 7) and if not a cloudcomputing node 10, then one or more general computing node that includesaspects of the cloud computing node 10.

In cloud computing node 10 there is a computer system/server 12, whichis operational with numerous other general purpose or special purposecomputing system environments or configurations. Examples of well-knowncomputing systems, environments, and/or configurations that may besuitable for use with computer system/server 12 include, but are notlimited to, personal computer systems, server computer systems, thinclients, thick clients, handheld or laptop devices, multiprocessorsystems, microprocessor-based systems, set top boxes, programmableconsumer electronics, network PCs, minicomputer systems, mainframecomputer systems, and distributed cloud computing environments thatinclude any of the above systems or devices, and the like.

Computer system/server 12 may be described in the general context ofcomputer system-executable instructions, such as program modules, beingexecuted by a computer system. Generally, program modules may includeroutines, programs, objects, components, logic, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Computer system/server 12 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 7, computer system/server 12 that can be utilized ascloud computing node 10 is shown in the form of a general-purposecomputing device. The components of computer system/server 12 mayinclude, but are not limited to, one or more processors or processingunits 16, a system memory 28, and a bus 18 that couples various systemcomponents including system memory 28 to processor 16.

Bus 18 represents one or more of any of several types of bus structures,including a memory bus or memory controller, a peripheral bus, anaccelerated graphics port, and a processor or local bus using any of avariety of bus architectures. By way of example, and not limitation,such architectures include Industry Standard Architecture (ISA) bus,Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnect (PCI) bus.

Computer system/server 12 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 12, and it includes both volatileand non-volatile media, removable and non-removable media.

System memory 28 can include computer system readable media in the formof volatile memory, such as random access memory (RAM) 30 and/or cachememory 32. Computer system/server 12 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 34 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 18 by one or more datamedia interfaces. As will be further depicted and described below,memory 28 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

Program/utility 40, having a set (at least one) of program modules 42,may be stored in memory 28 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. Program modules 42 generally carry out the functions and/ormethodologies of embodiments of the invention as described herein.

Computer system/server 12 may also communicate with one or more externaldevices 14 such as a keyboard, a pointing device, a display 24, etc.;one or more devices that enable a user to interact with computersystem/server 12; and/or any devices (e.g., network card, modem, etc.)that enable computer system/server 12 to communicate with one or moreother computing devices. Such communication can occur via Input/Output(I/O) interfaces 22. Still yet, computer system/server 12 cancommunicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 20. As depicted, network adapter 20communicates with the other components of computer system/server 12 viabus 18. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 12. Examples include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

It is to be understood that although this disclosure includes a detaileddescription on cloud computing, implementation of the teachings recitedherein are not limited to a cloud computing environment. Rather,embodiments of the present invention are capable of being implemented inconjunction with any other type of computing environment now known orlater developed.

Cloud computing is a model of service delivery for enabling convenient,on-demand network access to a shared pool of configurable computingresources (e.g., networks, network bandwidth, servers, processing,memory, storage, applications, virtual machines, and services) that canbe rapidly provisioned and released with minimal management effort orinteraction with a provider of the service. This cloud model may includeat least five characteristics, at least three service models, and atleast four deployment models.

Characteristics are as follows:

On-demand self-service: a cloud consumer can unilaterally provisioncomputing capabilities, such as server time and network storage, asneeded automatically without requiring human interaction with theservice's provider.

Broad network access: capabilities are available over a network andaccessed through standard mechanisms that promote use by heterogeneousthin or thick client platforms (e.g., mobile phones, laptops, and PDAs).Resource pooling: the provider's computing resources are pooled to servemultiple consumers using a multi-tenant model, with different physicaland virtual resources dynamically assigned and reassigned according todemand. There is a sense of location independence in that the consumergenerally has no control or knowledge over the exact location of theprovided resources but may be able to specify location at a higher levelof abstraction (e.g., country, state, or datacenter). Rapid elasticity:capabilities can be rapidly and elastically provisioned, in some casesautomatically, to quickly scale out and rapidly released to quicklyscale in. To the consumer, the capabilities available for provisioningoften appear to be unlimited and can be purchased in any quantity at anytime.

Measured service: cloud systems automatically control and optimizeresource use by leveraging a metering capability at some level ofabstraction appropriate to the type of service (e.g., storage,processing, bandwidth, and active user accounts). Resource usage can bemonitored, controlled, and reported, providing transparency for both theprovider and consumer of the utilized service.

Service Models are as follows:

Software as a Service (SaaS): the capability provided to the consumer isto use the provider's applications running on a cloud infrastructure.The applications are accessible from various client devices through athin client interface such as a web browser (e.g., web-based e-mail).The consumer does not manage or control the underlying cloudinfrastructure including network, servers, operating systems, storage,or even individual application capabilities, with the possible exceptionof limited user specific application configuration settings.

Platform as a Service (PaaS): the capability provided to the consumer isto deploy onto the cloud infrastructure consumer-created or acquiredapplications created using programming languages and tools supported bythe provider. The consumer does not manage or control the underlyingcloud infrastructure including networks, servers, operating systems, orstorage, but has control over the deployed applications and possiblyapplication hosting environment configurations.

Infrastructure as a Service (IaaS): the capability provided to theconsumer is to provision processing, storage, networks, and otherfundamental computing resources where the consumer is able to deploy andrun arbitrary software, which can include operating systems andapplications. The consumer does not manage or control the underlyingcloud infrastructure but has control over operating systems, storage,deployed applications, and possibly limited control of select networkingcomponents (e.g., host firewalls).

Deployment Models are as follows:

Private cloud: the cloud infrastructure is operated solely for anorganization. It may be managed by the organization or a third party andmay exist on-premises or off premises.

Community cloud: the cloud infrastructure is shared by severalorganizations and supports a specific community that has shared concerns(e.g., mission, security requirements, policy, and complianceconsiderations). It may be managed by the organizations or a third partyand may exist on-premises or off-premises.

Public cloud: the cloud infrastructure is made available to the generalpublic or a large industry group and is owned by an organization sellingcloud services.

Hybrid cloud: the cloud infrastructure is a composition of two or moreclouds (private, community, or public) that remain unique entities butare bound together by standardized or proprietary technology thatenables data and application portability (e.g., cloud bursting forload-balancing between clouds).

A cloud computing environment is service oriented with a focus onstatelessness, low coupling, modularity, and semantic interoperability.At the heart of cloud computing is an infrastructure that includes anetwork of interconnected nodes.

Referring now to FIG. 8, illustrative cloud computing environment 50 isdepicted. As shown, cloud computing environment 50 includes one or morecloud computing nodes 10 with which local computing devices used bycloud consumers, such as, for example, personal digital assistant (PDA)or cellular telephone 54A, desktop computer 54B, laptop computer 54C,and/or automobile computer system 54N may communicate. Nodes 10 maycommunicate with one another. They may be grouped (not shown) physicallyor virtually, in one or more networks, such as Private, Community,Public, or Hybrid clouds as described hereinabove, or a combinationthereof. This allows cloud computing environment 50 to offerinfrastructure, platforms and/or software as services for which a cloudconsumer does not need to maintain resources on a local computingdevice. It is understood that the types of computing devices 54A-N shownin FIG. 8 are intended to be illustrative only and that computing nodes10 and cloud computing environment 50 can communicate with any type ofcomputerized device over any type of network and/or network addressableconnection (e.g., using a web browser).

Referring now to FIG. 9, a set of functional abstraction layers providedby cloud computing environment 50 (FIG. 8) is shown. It should beunderstood in advance that the components, layers, and functions shownin FIG. 9 are intended to be illustrative only and embodiments of theinvention are not limited thereto. As depicted, the following layers andcorresponding functions are provided:

Hardware and software layer 60 includes hardware and softwarecomponents. Examples of hardware components include: mainframes 61; RISC(Reduced Instruction Set Computer) architecture based servers 62;servers 63; blade servers 64; storage devices 65; and networks andnetworking components 66. In some embodiments, software componentsinclude network application server software 67 and database software 68.

Virtualization layer 70 provides an abstraction layer from which thefollowing examples of virtual entities may be provided: virtual servers71; virtual storage 72; virtual networks 73, including virtual privatenetworks; virtual applications and operating systems 74; and virtualclients 75.

In one example, management layer 80 may provide the functions describedbelow. Resource provisioning 81 provides dynamic procurement ofcomputing resources and other resources that are utilized to performtasks within the cloud computing environment. Metering and Pricing 82provide cost tracking as resources are utilized within the cloudcomputing environment, and billing or invoicing for consumption of theseresources. In one example, these resources may include applicationsoftware licenses. Security provides identity verification for cloudconsumers and tasks, as well as protection for data and other resources.User portal 83 provides access to the cloud computing environment forconsumers and system administrators. Service level management 84provides cloud computing resource allocation and management such thatrequired service levels are met. Service Level Agreement (SLA) planningand fulfillment 85 provides pre-arrangement for, and procurement of,cloud computing resources for which a future requirement is anticipatedin accordance with an SLA.

Workloads layer 90 provides examples of functionality for which thecloud computing environment may be utilized. Examples of workloads andfunctions which may be provided from this layer include: mapping andnavigation 91; software development and lifecycle management 92; virtualclassroom education delivery 93; data analytics processing 94;transaction processing 95; and processing transactions in a database 96.

The present invention may be a system, a method, and/or a computerprogram product at any possible technical detail level of integration.The computer program product may include a computer readable storagemedium (or media) having computer readable program instructions thereonfor causing a processor to carry out aspects of the present invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, configuration data for integrated circuitry, oreither source code or object code written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Smalltalk, C++, or the like, and procedural programminglanguages, such as the “C” programming language or similar programminglanguages. The computer readable program instructions may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider). In some embodiments, electronic circuitry including,for example, programmable logic circuitry, field-programmable gatearrays (FPGA), or programmable logic arrays (PLA) may execute thecomputer readable program instructions by utilizing state information ofthe computer readable program instructions to personalize the electroniccircuitry, in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the blocks may occur out of theorder noted in the Figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a”, “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willbe further understood that the terms “comprises” and/or “comprising”,when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, if any, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of one or more embodiments has been presentedfor purposes of illustration and description, but is not intended to beexhaustive or limited to in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the art. Theembodiment was chosen and described in order to best explain variousaspects and the practical application, and to enable others of ordinaryskill in the art to understand various embodiments with variousmodifications as are suited to the particular use contemplated.

What is claimed is:
 1. A computer-implemented method, comprising:maintaining, by one or more processors, a current version of at least apart of a database in a file associated with a mass storage device,wherein the file comprises content; mapping, by the one or moreprocessors, at least a portion of the content of the file to an addressregion; obtaining, by the one or more processors, a command to open anew transaction; based on obtaining the command, generating, by the oneor more processors, a cloned version of the address region; and mapping,by the one or more processors, one or more files associated with themass storage device comprising the database to the clones version of theaddress region.
 2. The computer-implemented method of claim 1, furthercomprising: obtaining, by the one or more processors, a commit command;based on obtaining the commit command, determining, by the one or moreprocessors, that the cloned version of the address region and the mappedone or more files reflect a new current of the at least part of thedatabase.
 3. The computer-implemented method of claim 1, furthercomprising: obtaining, by the one or more processors, a rollbackcommand;
 4. The computer-implemented method of claim 3, furthercomprising: based on obtaining the rollback command, discarding, by theone or more processors, the cloned version of the address region and theone or more files associated with the mass storage device.
 5. Thecomputer-implemented method of claim 1, wherein the address regioncomprises a processor address region.
 6. The computer-implemented methodof claim 1, wherein mapping the one or more files comprises mapping acurrent state of the database.
 7. The computer-implemented method ofclaim 1, wherein the state of the database comprises all temporarymodifications done by transactions owning the address region.
 8. Thecomputer-implemented method of claim 1, wherein each mapped file of theone or more mapped files represents the address region from aperspective of a transaction.
 9. The computer-implemented method ofclaim 1, wherein persistent storage comprises the address region.
 10. Acomputer program product comprising: a computer readable storage mediumreadable by one or more processors and storing instructions forexecution by the one or more processors for performing a methodcomprising: maintaining, by the one or more processors, a currentversion of at least a part of a database in a file associated with amass storage device, wherein the file comprises content; mapping, by theone or more processors, at least a portion of the content of the file toan address region; obtaining, by the one or more processors, a commandto open a new transaction; based on obtaining the command, generating,by the one or more processors, a cloned version of the address region;and mapping, by the one or more processors, one or more files associatedwith the mass storage device comprising the database to the clonesversion of the address region.
 11. The computer program product of claim10, further comprising: obtaining, by the one or more processors, acommit command; based on obtaining the commit command, determining, bythe one or more processors, that the cloned version of the addressregion and the mapped one or more files reflect a new current of the atleast part of the database.
 12. The computer program product of claim10, further comprising: obtaining, by the one or more processors, arollback command;
 13. The computer program product of claim 12, furthercomprising: based on obtaining the rollback command, discarding, by theone or more processors, the cloned version of the address region and theone or more files associated with the mass storage device.
 14. Thecomputer program product of claim 10, wherein the address regioncomprises a processor address region.
 15. The c computer program productof claim 10, wherein mapping the one or more files comprises mapping acurrent state of the database.
 16. The computer program product of claim10, wherein the state of the database comprises all temporarymodifications done by transactions owning the address region.
 17. Thecomputer program product of claim 10, wherein each mapped file of theone or more mapped files represents the address region from aperspective of a transaction.
 18. A system comprising: one or morememories; one or more processors in communication with the one or morememories; and program instructions executable by the one or moreprocessors via the one or more memories to perform a method, the methodcomprising: a computer readable storage medium readable by one or moreprocessors and storing instructions for execution by the one or moreprocessors for performing a method comprising: maintaining, by the oneor more processors, a current version of at least a part of a databasein a file associated with a mass storage device, wherein the filecomprises content; mapping, by the one or more processors, at least aportion of the content of the file to an address region; obtaining, bythe one or more processors, a command to open a new transaction; basedon obtaining the command, generating, by the one or more processors, acloned version of the address region; and mapping, by the one or moreprocessors, one or more files associated with the mass storage devicecomprising the database to the clones version of the address region. 19.The system of claim 18, the method further comprising: obtaining, by theone or more processors, a commit command; based on obtaining the commitcommand, determining, by the one or more processors, that the clonedversion of the address region and the mapped one or more files reflect anew current of the at least part of the database.
 20. The system ofclaim 18, the method further comprising: obtaining, by the one or moreprocessors, a rollback command; and based on obtaining the rollbackcommand, discarding, by the one or more processors, the cloned versionof the address region and the one or more files associated with the massstorage device.